Erm.. the radial cannon and riot shotgun.. you wouldn't be able to see the projectiles very well because they're not designed to be slow-moving projectiles. The riot shotgun is hitscan, and on occasion you can see the shells bouncing off the walls, but certainly not all the time. The radial cannon primary you may be able to make out, it travels very quickly, but you can see the grey shells. The secondary is hitscan, so you wouldn't really see anything in the air.
It's all in the readme:
* Radial Cannon - Primary shoots flak in a very tight bunch at high speed, you should decimate someone with this in one shot. Secondary launches a hitscan mortar that usually kills outright, but if not bounces the enemy around slightly.
Do you see the radial cannon secondary explosion on the place you hit, btw?